An earthquake is the sudden vibration of the earth’s surface by rapid release of energy. This energy is released when two parts of rock masses move suddenly in relation to each other along a fault.
Causes of Earthquake
Depending upon their mode of origin, the EQ are classified into following groups.
i. EQ Due to Surface Causes
EQ may be generated by landslips and collapse of the roof of underground caverns; most of these are very minor
ii. EQ Due to Volcanic Causes
Volcanic eruptions may also produce EQ but such earthquakes are generally very feeble.
iii. EQ Due to Tectonic Causes
Tectonic EQs are the most numerous and unusually the most disastrous. They are caused by shocks with originate in the earth’s crust due to sudden movement along faults.
One the basic of the depth the focus, the earthquakes are divided into the following groups.
iv. Shallow Focus Earthquakes
Earthquakes having depth of focus upto 55 km.
v. Intermediate Focus Earthquakes
Earthquake having depth of focus 55-300km.
vi. Deep Focus Earthquakes
Earthquake having depth of focus 300-650km
Effects of Earthquake
v Buildings are damaged and people get frightened.
v Roads are fissured, railway lines are twisted and brides are destroyed.
v In cities, ground waves disrupt underground services and start fires.
v Rivers change their courses; Fissures are opened up in the ground which may cause spring.
v Permanent tilting of the land mass may occur in certain areas. Landslides may occur in hilly regions.